Optical packet switching apparatus

Abstract

An optical packet switching apparatus includes an optical coupler, an optical switch unit, and an optical switch control unit. The optical switch control unit includes an optical-to-electrical converter, a serial/parallel converter, an arrangement detector, a rearrangement unit, a frame synchronization unit, a route detector, a control signal generator, and an adjustment unit for adjusting the timing with which to output an optical switch control signal to the optical switch unit, based on arrangement information on a frame synchronization pattern fed from the arrangement detector.

What is claimed is: 
     
       1. An optical packet switching apparatus comprising:
 a branching unit configured to branch off a received optical packet signal; 
 an optical switch unit configured to switch a route of one of the branched-off optical packet signal so as to output the optical packet signal; and 
 an optical switch control unit configured to extract routing information from an other of the branched-off optical packet signal and configured to control the optical switching unit according to the extracted routing information, 
 the optical switch control unit including:
 an optical-to-electrical (O/E) converter configured to convert the other of the branched-off optical packet signal into an electrical data signal and configured to extract a clock signal from the electrical data signal; 
 a serial/parallel converter configured to perform a serial/parallel conversion of the electrical data signal into a parallel data signal and configured to divide the frequency of the clock signal so as to generate a divided clock signal; 
 an arrangement detector configured to detect an arrangement of a frame synchronization pattern contained in the parallel data; 
 a rearrangement unit configured to rearrange the parallel data signal based on detected arrangement information on the frame synchronization pattern; 
 a frame synchronization unit configured to establish frame synchronization based on the frame synchronization pattern contained in the rearranged parallel data signal; 
 a route detector configured to detect routing information contained in the rearranged parallel data signal after the frame synchronization has been established; 
 a generator configured to generate an optical switch control signal used to control the optical switch unit based on the detected routing information; and 
 an adjustment unit configured to adjust output timing with which to output the optical switch control signal to the optical switch unit, based on the arrangement information on the frame synchronization pattern. 
 
 
     
     
       2. The optical packet switching apparatus according to  claim 1 , wherein the adjustment unit generates a plurality of optical switch control signals whose output timings differ, and configured to select one from among the plurality of optical switch control signals, based on the arrangement information on the frame synchronization pattern. 
     
     
       3. The optical packet switching apparatus according to  claim 2 , wherein the optical switch control unit generates the plurality of optical switch control signals, using a multiplication clock signal in which a local clock signal fed from a local oscillator is multiplied. 
     
     
       4. The optical packet switching apparatus according to  claim 1 , the optical switch control unit further including:
 a local oscillator configured to oscillate a local clock signal; 
 a clock transfer unit configured to perform a transfer from the parallel data signal synchronized with the divided clock signal, to the local clock signal; 
 a phase difference detector configured to detect a phase difference between the divided clock signal and the local clock signal; and 
 a second adjustment unit configured to adjust the output timing of the optical switch control signal, based on information on the phase difference. 
 
     
     
       5. The optical packet switching apparatus according to  claim 4 , the phase difference detector including:
 a first edge detector for performing differential edge detection on a rising edge or falling edge of the divided clock signal; 
 a second edge detector for performing differential edge detection on a rising edge or falling edge of the local clock signal; and 
 a phase difference determining unit for determining a difference in phase between an output pulse from the first edge detector and that from the second edge detector. 
 
     
     
       6. The optical packet switching apparatus according to  claim 4 , the phase difference detector including:
 a first exclusive-OR computing unit for computing exclusive-OR of the divided clock signal and the local clock signal; 
 a second exclusive-OR computing unit for computing exclusive-OR of a clock signal, which lags one of the divided clock signal and the local clock signal by the phase of 90 degrees, and an other of the clock signals; and 
 a phase difference determining unit for determining a difference in phase between the divided clock signal and the local clock signal, based on duty ratios of an output from the first exclusive-OR computing unit and an output from the second exclusive-OR computing unit. 
 
     
     
       7. The optical packet switching apparatus according to  claim 4 , the phase difference detector including:
 a first logical AND computing unit for computing logical AND of the divided clock signal and the local clock signal; 
 a second logical AND computing unit for computing logical AND of a clock signal, which lags one of the divided clock signal and the local clock signal by the phase of 90 degrees, and the other of the clock signals; and 
 a phase difference determining unit for determining a difference in phase between the divided clock signal and the local clock signal, based on duty ratios of an output from the first logical AND computing unit and an output from the second logical AND computing unit. 
 
     
     
       8. The optical packet switching apparatus according to  claim 4 , the phase difference detector including:
 a first logical OR computing unit for computing logical OR of the divided clock signal and the local clock signal; 
 a second logical OR computing unit for computing logical OR of a clock signal, which lags one of the divided clock signal and the local clock signal by the phase of 90 degrees, and an other of the clock signals; and 
 a phase difference determining unit for determining a difference in phase between the divided clock signal and the local clock signal, based on duty ratios of an output from the first logical OR computing unit and an output from the second logical OR computing unit. 
 
     
     
       9. An optical packet switching apparatus comprising:
 a branching unit configured to branch off a received optical packet signal; 
 an optical switch unit configured to switch a route of one of the branched-off optical packet signal so as to output the optical packet signal; and 
 an optical switch control unit configured to extract routing information from an other of the branched-off optical packet signal and configured to control the optical switching unit according to the extracted routing information, 
 the optical switch control unit including:
 an optical-to-electrical (O/E) converter configured to convert the other of the branched off optical packet signal into an electrical data signal and configured to extract a clock signal from the electrical data signal; 
 a serial/parallel converter configured to perform a serial/parallel conversion of the electrical data signal into a parallel data signal and configured to divide the frequency of the clock signal so as to generate a divided clock signal; 
 a local oscillator configured to oscillate a local clock signal; 
 a clock transfer unit configured to perform a transfer from the parallel data signal synchronized with the divided clock signal, to the local clock signal; 
 a route detector configured to detect the routing information contained in the parallel data signal; 
 a generator configured to generate an optical switch control signal used to control the optical switch unit based on the detected routing information; 
 a phase difference detector configured to detect a phase difference between the divided clock signal and the local clock signal; and 
 an adjustment unit configured to adjust output timing of the optical switch control signal, based on information on the phase difference fed from the phase difference detector. 
 
 
     
     
       10. The optical packet switching apparatus according to  claim 9 , wherein the adjustment unit generates a plurality of optical switch control signals whose output timings differ, and configured to select one from among the plurality of optical switch control signals, based on the phase difference information. 
     
     
       11. The optical packet switching apparatus according to  claim 10 , the optical switch control unit further including a clock multiplication unit configured to multiply the local clock signal,
 wherein the adjustment unit generates the plurality of optical switch control signals, using a multiplication clock signal supplied from the clock multiplication unit. 
 
     
     
       12. The optical packet switching apparatus according to  claim 9 , the phase difference detector including:
 a first edge detector for performing differential edge detection on a rising edge or falling edge of the divided clock signal; 
 a second edge detector for performing differential edge detection on a rising edge or falling edge of the local clock signal; and 
 a phase difference determining unit for determining a difference in phase between an output pulse from the first edge detector and that from the second edge detector. 
 
     
     
       13. The optical packet switching apparatus according to  claim 9 , the phase difference detector including:
 a first exclusive-OR computing unit for computing exclusive-OR of the divided clock signal and the local clock signal; 
 a second exclusive-OR computing unit for computing exclusive-OR of a clock signal, which lags one of the divided clock signal and the local clock signal by the phase of 90 degrees, and an other of the clock signals; and 
 a phase difference determining unit for determining a difference in phase between the divided clock signal and the local clock signal, based on duty ratios of an output from the first exclusive-OR computing unit and an output from the second exclusive-OR computing unit. 
 
     
     
       14. The optical packet switching apparatus according to  claim 9 , the phase difference detector including:
 a first logical AND computing unit for computing logical AND of the divided clock signal and the local clock signal; 
 a second logical AND computing unit for computing logical AND of a clock signal, which lags one of the divided clock signal and the local clock signal by the phase of 90 degrees, and the other of the clock signals; and 
 a phase difference determining unit for determining a difference in phase between the divided clock signal and the local clock signal, based on duty ratios of an output from the first logical AND computing unit and an output from the second logical AND computing unit. 
 
     
     
       15. The optical packet switching apparatus according to  claim 9 , the phase difference detector including:
 a first logical OR computing unit for computing logical OR of the divided clock signal and the local clock signal; 
 a second logical OR computing unit for computing logical OR of a clock signal, which lags one of the divided clock signal and the local clock signal by the phase of 90 degrees, and an other of the clock signals; and 
 a phase difference determining unit for determining a difference in phase between the divided clock signal and the local clock signal, based on duty ratios of an output from the first logical OR computing unit and an output from the second logical OR computing unit.